The Staten Island mom murdered during a dream vacation alone in Istanbul likely fought for her life before her skull was crushed, according to Turkish news reports.

Istanbul investigators yesterday revealed that Sarai Sierra, 33, was killed by a single blow to the head, as they released her body to a local Armenian Catholic church and the FBI joined the investigation, authorities said.

Investigators also turned over DNA samples to a crime lab for testing — including scrapings from Sierra’s fingernails, which indicate she tried to fight her killer, the Milliyet newspaper reported.

Residents lined sidewalks as Sierra’s chipped, wooden casket was carried through streets lined with food and spice stalls to the Surp Yerrortutyun church. The church will remained closed while her body is inside, officials told Turkey’s Hurriyet Daily News.

Sierra’s husband, Steven — who flew to Istanbul to look for her after the amateur photographer failed to show up for a Jan. 21 flight home to New York — did not join the procession, authorities said.

“I wanted to see my daughter alive. At least we have closure; at least they found her,” Sierra’s heartsick mom, Betzaida Jimenez, said yesterday at her Staten Island home.

“I hugged her before she left. I said to her, ‘Let’s pray together for your safety.’ Just the thought that I’ll never be able to hug her again, it’s hard,” she said.

Family members said they are waiting until Steven comes back with his wife’s body, likely later this week, before telling the couple’s two boys, ages 9 and 11, that their mother is dead.

Rep. Michael Grimm said the FBI is playing a “significant” role in the murder investigation.

Sierra flew to Istanbul Jan. 7, and then went to Amsterdam and Munich before returning to Turkey.

Her body was found Feb. 2 near ancient walls in the city’s Sarayburnu neighborhood. There was no sign of sexual assault, Istanbul authorities said.

Prosecutors yesterday got a warrant to take blood and saliva samples from 21 people.

Ulgutol disputed previous reports that Sierra had blown through nearly $15,000 on her two-week trip, saying she spent “reasonably” for a tourist and that her husband had sent her $500 while she was gone.

Sierra was still wearing a gold ring, wristband and necklace when she was found. Her Samsung Galaxy phone and iPad — which she used to take her pictures — are missing. Interpol is tracking her overseas e-mail correspondence.